open roadside on coarse granitic roadbed mixed over substrate of volcanic tuff and tuffaceous rhyolite at crest of the eastern escarpment onto Madrean plateau. This species is largely distinguished with difficulty from C. pringlei by a 2 cm difference in maximum width of the flowering heads which make photo determination impossible and pressed specimen difficult, without careful in-field measurements of live mature heads. In most cases I have placed these similar plants under C. palmer, the slightly smaller and more common of the two species.
